The present invention relates to a method for obtaining a trabecular index using a trabecular pattern and a method for estimating a bone mineral density using trabecular indices.
Osteoporosis is a wide spread medical condition that affects the middle-aged and older populations. Especially, the condition is prevalent in postmenopausal women. Osteoporosis is characterized by an abnormal loss in bone mineral content, which leads to a tendency toward non-traumatic bone fractures and to structural deformations of bones. However, effective therapy for osteoporosis has not been developed yet. Only several methods for reducing the occurrence possibility of osteoporosis through physical exercises or appropriate diets are known. Accordingly, it is important that a method for easily and inexpensively diagnosing the osteoporosis should be developed for the prevention of deterioration of osteoporosis and early stage treatment of osteoporosis.
Bone mineral density measurement is basic for diagnosing osteoporosis because osteoporosis is characterized by an abnormal loss in bone mineral content. Various methods have been developed for the quantitative measurement of bone mineral density. The most widely used method for measuring bone mineral density is dual photon absorptiometry with either an X-ray or nuclear source. The accuracy error of this method in determining bone mineral content is reported to be about few percentages. Quantitative computed tomography provides a three-dimensional bone density assessment and separate estimations of cortical and trabecular bone densities. However, the routine use of these bone densitometries is precluded by their high costs.
Mechanical strength of the whole bone is determined mainly by the dense cortical part. However, many investigators have indicated that the trabecular bone is also an important factor in determining mechanical strength of bone. Moreover, it is well known that the trabecular bone is resorbed more rapidly than cortical bone in osteoporosis. This implies that the trabecular bone is more reflective of the stage of osteoporosis and that early stage intervention in osteoporosis can be possible through an evaluation of changes in trabecular bone. In this sense, many investigators have studied trabecular patterns appearing on conventional X-ray images. As clinical tools for assessing changes in trabecular patterns of X-ray images, Saville""s and Singh""s indices are available. These indices assess stages of osteoporosis using trabecular patterns changes appearing on X-ray images of the lateral lumbar spine and the upper part of the femur. In computerized image processing approach, various textural measures such as gray level statistics, frequency domain analysis, and fractal dimension analysis have been applied to quantify changes of trabecular pattern. These methods are reported to be somewhat successful to anticipate fracture risks of bone. But they do not provide trabecular indices well correlated with quantitative bone mineral density.
It is, therefore, an object of the present invention to provide a method for obtaining a trabecular index using a trabecular pattern of an X-ray image and a computer-readable medium for performing the method.
It is another object of the present invention to provide a method for obtaining a trabecular index by quantifying changes in a trabecular pattern appearing on an X-ray image and a computer-readable medium for performing the method.
It is further another object of the present invention to provide a method for estimating a bone mineral density using trabecular indices and a computer-readable medium for performing the method.
In accordance with an aspect of the present invention, there is provided a method for obtaining a trabecular index using a trabecular pattern in a computer, comprising the steps of: (a) obtaining an X-ray image of a bone; (b) determining a region of interest on the X-ray image; (c) dividing the region of interest into a plurality of blocks including a plurality of pixels; (d) calculating a gray level of each pixel; (e) scaling gray levels of the pixels for each block with a linear function; (f) calculating an average gray level of each block; and (g) obtaining the trabecular index by re-averaging the average gray levels for the blocks.
In accordance with another aspect of the present invention, there is provided a method for estimating a target bone mineral density using a target trabecular index in a computer, comprising the steps of: (a) obtaining X-ray images of sample bones; (b) determining regions of interest on the X-ray images; (c) obtaining a trabecular index corresponding to each region of interest; (d) measuring a bone mineral density of each sample with a bone densitometer; (e) obtaining a functional relation between the trabecular index and the bone mineral density; and (f) estimating the target bone mineral density using the target trabecular index related to a target bone from the functional relation.
In accordance with further another aspect of the present invention, there is provided a computer-readable medium for performing the steps. of: (a) obtaining an X-ray image of a bone; (b) determining a region of interest on the X-ray image; (c) dividing the region of interest into a plurality of blocks including a plurality of pixels; (d) calculating a gray level of each pixel; (e) scaling gray levels of the pixels for each block with a linear function; (f) calculating an average gray level of each block; and (g) obtaining the trabecular index by re-averaging the average gray levels for the blocks.
In accordance with furthermore another aspect of the present invention, there is provided a computer-readable medium for performing the steps of: (a) obtaining X-ray images of sample bones; (b) determining regions of interest on the X-ray images; (c) obtaining a trabecular index corresponding to each region of interest; (d) measuring a bone mineral density of each sample with a bone densitometer; (e) obtaining a functional relation between the trabecular index and the bone mineral density; and (f) estimating a target bone mineral density using a target trabecular index related to a target bone from the functional relation.